Traditionally, impedance derived measures of cardiac autonomic balance (CAB) and regulation (CAR) are calculated using indices of heart rate variability (HRV) that primarily reflect parasympathetic nervous system activity (e.g., high-frequency HRV | HF-HRV or HF) and pre-ejection period (PEP; a systolic time interval and measure of sympathetic activity). However, HF-HRV and PEP are considered measures of chronotropic and inotropic cardiac influence, respectively. Left ventricular ejection time (LVET) is a systolic time interval that reflects sympathetic chronotropic influence, and therefore may be a more appropriate measure for calculating CAB and CAR compared to PEP. Thus, the current study evaluates both PEP and LVET in the calculation of CAB and CAR. Data from 158 healthy participants (mean age = 19.09 years old, SD = 1.84 years) were available for analyses. CAB and CAR values were calculated using both HF-HRV and the root mean square of successive differences (RMSSD), in addition to both PEP and LVET, in accordance with previously established guidelines. Analyses showed that correlations were significantly weaker between CAB and CAR calculated using LVET for both HF (z = 5.12, p < .001) and RMSSD (z = 5.26, p < .001) than with PEP. These data suggest that LVET, compared to PEP, provides better “autonomic space” as evidenced by a lack of correlation between CAB and CAR computed using LVET. We stress that future research consider calculating CAB and CAR using chronotropic measures for both parasympathetic and sympathetic activity, as doing so may yield more accurate and independent measures of cardiac autonomic activity compared to a mixture of inotropic (i.e., PEP) and chronotropic (i.e., HF-HRV) measures.

Ethnic disparities in physical health outcomes have been a pressing public health concern for decades, with African Americans (AAs) displaying disproportionately higher rates of morbidity and mortality from prominent communicable (e.g., infectious) and chronic (e.g., cardiovascular) diseases compared to European Americans (EAs). Importantly, higher levels of emotional (e.g., positive affect) and social (e.g., social support) well-being factors have generally been linked with better physical functioning and health, but there remains a lack of research exploring if their psychological and physiological downstream effects on health may vary based on ethnicity. Thus, the current dissertation sought to explore AA and EA differences in physiological pathways implicated in health as well as determine if emotional and social well-being factors were differentially linked with physical health measures and outcomes. Study 1 is a systematic review and meta-analysis that examined differences in baseline levels of common inflammatory measures between AAs and EAs. Study 2 is a secondary data analysis of viral exposure studies that explored whether common emotional well-being factors were equally protective against upper respiratory infections in a localized sample of AAs and EAs. Study 3 built on Study 2 by investigating potential differences in the benefits of social well-being factors on physiological measures of cardiovascular functioning and diagnosed cardiovascular health outcomes in a nationally representative sample of AAs and EAs.

Results from Study 1 indicated that AAs generally had higher resting levels of pro-inflammatory factors (e.g., C-reactive protein), while EAs generally had higher resting levels of anti-inflammatory factors (e.g., Interleukin-10). Results from Study 2 revealed that emotional well-being factors (e.g., positive affect, self-esteem) were associated with a reduced risk of infection after experimental virus exposure for EAs, but for AAs the same factors were either unrelated or associated with an increased risk of infection. Results from Study 3 showed that certain social well-being factors (e.g., social acceptance) were cardioprotective (e.g., linked with lower mean arterial pressure) for AAs but not EAs, while other factors (e.g., social contribution) were cardioprotective (e.g., linked with fewer diagnosed cardiovascular ailments) for EAs but not AAs. The current findings collectively provide evidence of marked ethnic differences in key biomarkers of physical health and suggest that positive psychological factors may be differentially protective against negative cardiovascular and immune outcomes in AAs and EAs, offering critical implications for ethnic health disparities.